1. Field of the Invention
The present invention relates to a method for producing a liquid crystal cell substrate and a method for producing a liquid crystal panel.
2. Description of Related Art
Conventionally, birefringent layers for optical compensation in various liquid crystal displays have been formed by stretching and orienting a polymer film or fixing orientation of a liquid crystal compound or a liquid crystal polymer.
Furthermore, U.S. Pat. Nos. 5,344,916, 5,395,918, 5,480,964, 5,580,950, 5,694,187 and 5,750,641 disclose a production method of coating an inorganic compound base (an SUS belt, a copper sheet, a glass sheet, an Si wafer or the like) with a polymer such as polyamide, polyimide, polyester, polyetherketone, polyamide imide or polyesterimide and a method for producing an optical retardation film serving as a negative birefringent layer by coating an Si wafer with polyimide.
Moreover, U.S. Pat. No. 6,074,709 discloses a production method of laminating a polyimide layer on a support such as a glass sheet, an optically isotropic polymer layer, an anisotropic polymer layer or an anisotropic ceramic layer.
For providing the birefringent layer produced as above in a liquid crystal display, the birefringent layer is integrated with a polarizing plate and then attached to a liquid crystal cell or attached to external sides of substrates that sandwich a liquid crystal. Further, U.S. Pat. No. 5,907,378 and U.S. Pat. No. 6,028,651 have reported that a birefringent layer formed of polyimide is attached to internal sides of substrates that sandwich a liquid crystal, and serves as both an oriented film and a birefringent layer.
However, providing such a birefringent layer formed of polyimide or the like in a liquid crystal cell usually requires complicated processes because an integrated layer of the birefringent layer and the polarizing plate is formed first and then attached to external sides of the cell via a sticking agent. Consequently, there has been a problem of an increased overall thickness. Also, there has been a problem that, when the birefringent layer formed of polyimide or the like is attached onto the cell via an adhesive, the birefringent layer peels off by heat.
Additionally, in the case of forming a birefringent layer serving as both an oriented film and a birefringent layer on the internal sides of the cell, since a currently available material has a small birefringence with respect to thickness, such a layer needs to have a thickness of at least 1 xcexcm to function as a birefringent layer. In this case, a natural modulus of elasticity of the film not only causes an adjusting agent to fill up in the film at the time of adjusting a cell gap and, thus, a gap adjustment cannot be made, but also changes the retardation of the birefringent layer, so that uniformity is lost, which causes the problem that an actual use is extremely difficult.
In order to achieve the above-mentioned object, the present invention provides a method for producing a liquid crystal cell substrate including a base and a birefringent layer. The method includes producing a precursor layer of the birefringent layer by applying a solution of a polymer that hardens to form the birefringent layer, directly onto one surface of the base, and producing the birefringent layer by hardening the precursor layer.
Also, the present invention provides a method for producing a liquid crystal panel having a birefringent layer on one of surfaces of a liquid crystal cell. The method includes preparing the liquid crystal cell including two liquid crystal cell substrates and a liquid crystal layer interposed between the two liquid crystal cell substrates, producing a precursor layer of the birefringent layer by applying a solution of a polymer that hardens to form the birefringent layer, directly onto at least one surface of the two liquid crystal cell substrates, and producing the birefringent layer by hardening the precursor layer.